The present invention relates to an arrangement for the supply of pressure to brake slip (antiskid) control apparatus during braking operations in automotive vehicles including a source of pressure to supply the necessary control pressure in the wheel brake cylinders.
The basic principle of current brake slip control apparatuses include increasing, decreasing, or maintaining constant, the pressure in the wheel brake cylinders in a specific sequence. This is termined a brake control or philosophy. The control commands are generated by an electronic control unit connected to wheel velocity sensors and are issued to appropriate control units if excessive slip values between vehicle tires and road surface are detected. First, it is known to have the control pressure generated by a separate hydraulic pump and a hydraulic accumulator communicating with the pump. Further, it is also known to charge an accumulator which is provided with a pressure-operated switch by a power steering pump already available in the motor vehicle, so that the control pressure is available should the necessity for a brake control action arise. While the control pressure generating structure initially referred to necessities high constructional expenditure and corresponding manufacturing cost, it is considered a disadvantage in the second control pressure generating arrangement described that the steering behavior of the automotive vehicle may change if the power steering pump is bled during a controlled braking action.
Accordingly, in the known systems the control pressure required for a controlled braking action is held available at all times althrough braking operations assisted by the brake slip control apparatus occur at only very large intervals. It is assumed that the operator of an automotive vehicle equipped with a brake slip control apparatus, driving normally in weather conditions usual in the temperate zone and under normal vehicle operating conditions, is required to utilize his brake slip control apparatus only every 5,000 km (kilometers) on an average.
Further, special restraint systems to protect the occupants of automotive vehicles have become known, for instance German Patent DE-AS No. 2,163,919, including essentially an inflatable bag which in the event of a collision is filled with gas within an extremely short period of time to thereby provide an impact protection for the vehicle occupants from the windshield or from parts of the interior trim of the vehicle. In the restraint systems described, the gas required to inflate the bag is produced by a chemical propellant which is, for example, ignited by a deceleration sensor fitted to the vehicle.